1. Field of the Invention
The invention is in the general field of Wireless LAN and directional antenna alignment devices and methods.
2. Description of the Related Art
In recent years, a variety of high-speed short range digital radio transceiver devices, in particular wireless local area network (Wireless-LAN or WLAN) devices, and Wireless Personal Area Network (WPAN) devices have become ubiquitous in the modern world. These devices originally assigned to the unlicensed frequency bands such as 2.4 GHz, 900 MHz and later in the 5 Gigahertz region and originally intended for ranges of up to only a few hundred feet, are now so prevalent that the costs for these system chipsets are now down to only a few dollars each.
These Wireless-LAN standards were originally based on the IEEE 802.11 standard, other related short range LAN and PAN standards, such as the IEEE 802.15 (Bluetooth™) and 802.15.4 (Zigbee™) standards have also become popular. Due to the extremely large market for these devices, chipsets capable of implementing these standards as well are also available for only a few dollars each. Like 802.11, these later standards also were originally intended for distances of at most a few hundred feet.
Although a number of long range digital radio transceiver devices (Wireless-Wide Area Networks or WAN)) originally designed for link distances of many miles or more have been developed, the number of devices that implement such long distance standards are orders of magnitude less than the nearly ubiquitous IEEE 802.11 Wi-Fi chips and related 802.15 (Bluetooth) and 802.15.4 (Zigbee standards).
Although some parts of the IEEE 802.11 standards incorporate certain timing constraints related to assumptions involving the time that light (radio signals) take to travel over short range distances, as well as certain assumptions about power levels, and frequencies, the 802.11 standard is otherwise relatively general-purpose and robust. As a result, workers have found that with some software adjustments (for example adjustments that increase window times to account for speed-of-light lag over longer distances), as well as larger and more directional antenna, the ultra-low cost chipsets and electronics originally developed to send digital data signals only a few hundred feet can be modified to send signals over many miles. This makes it possible to use modified Wireless-LAN technology to bring the benefits of long-distance broadband Internet and other modern digital communications technology to rural areas at a cost that is only a small fraction of that of alternate approaches.
As a result, extremely inexpensive Wireless-LAN based access points, relay stations, and user stations are starting to become very popular, and can deliver coverage to lower income and rural areas that otherwise could not afford any alternate form of digital communications or Internet connectivity.
One problem with setting up such modified or “hacked” IEEE 802.11 Wireless-LAN based long distance communications, however is that in order to allow what is essentially short-range equipment and standards to operate over far longer ranges than originally intended, the antennas (on both ends of the communications link) must be fairly large and highly directional. The directional antennas help focus the relatively weak Wireless-LAN radio beam (which often may have RF radio power of at most 1 Watt) and ensure that the low energy radio signals are transmitted to the target, which may be miles away, with enough signal intensity. On the other end, the target in turn often uses large directional antennas to pick up the relatively weak Wireless-LAN signal.
Because both antennas are both highly directional, and must be precisely oriented over distances many miles or more, the difficulties of aligning the directional transmitting and receiving antenna should be appreciated, particularly within the severe budgetary constraints that mandate use of modified or “hacked” IEEE 802.11 equipment for long distance communications in the first place.
At present, prior art methods often involve a tedious process in which an installer climbs onto the structure holding the antenna, talks via a mobile phone or a second set of two-way radios with a counterpart at the other end of the link, and the two manually adjust the antennas and assess the signal strength and signal quality of the link.
For example, Cisco systems, a leading manufacturer of outdoor radios, in Appendix “C”, “Antenna Basics” of their “Cisco Aironet 350 Series Bridge Hardware Installation Guide, page C-5 to C-6” recommends their installation professionals carry GPS tools & compasses to help with alignment on their Aironet 350 series outdoor WiFi radios.
Another popular alignment aid supplied by equipment manufacturers is alignment equipment that has LED indicators that are visible to an installer. In this scheme, a stronger signal illuminates more LED lights. For example, Ubiquiti Networks, a manufacturer of outdoor Wi-Fi radios, has provided such LED lights to help with alignment on their Nanostation2 (Ubiquiti Networks NanoStation2 Datasheet, page 2).
A third alignment aid found in other prior art alignment equipment includes a sound synthesizer that generates a sound signal whose amplitude is proportional to the signal strength. For example, Trango Systems uses such audio aid in their TrangoLINK-45™ outdoor Wi-Fi radio (TrangoLINK-45 data sheet)
Additionally, regulatory requirements also require that these installers be qualified professionals, which adds additional cost to this process. The end result is both dangerous to the workers, and not fully satisfactory under all conditions, because unless the structure that the directional antenna is bolted to is quite sturdy, with time the antenna alignment can drift to an unsatisfactory position. Such drift in alignment would not only require a professional installer's service for alignment, but also cause down time to the network till the availability of such an installer.
Although prior art methods for automatically steering satellite antennas and other non-Wireless-LAN directional antennas, exemplified by U.S. Pat. Nos. 4,841,309, 5,214,364, 6,049,306, 6,850,202, 6,864,847, and 7,633,893 are known, these methods tend to be both elaborate and expensive, and are not well suited for the ultra-low cost demands of long distance telecommunications using modified or “hacked” versions of the IEEE 802.11 (Wi-Fi) standard, and its related standards such as 802.15 (Bluetooth) and 802.15.4 (Zigbee) standards. Thus further advances are desirable.